Method and system for an optical connection service interface

ABSTRACT

Methods and systems for an optical connection service interface may include, in an optical data link comprising an optical fiber, a local control system, first and second transceivers at ends of the optical fiber, generating a signal for the local control system at a low frequency and communicating, utilizing the optical fiber, an optical data signal at a high frequency and an Optical Connection Service interface (OCSi) signal at an intermediate frequency. An optical signal may be modulated at the intermediate frequencies for the OCSi, and may be modulated and communicated to the second transceiver. The communicated modulated signal and the optical data signal may be detected utilizing a photodetector in the second transceiver. The detected optical signal may be demodulated, and an optical power of the optical data signal may be configured based on the demodulated signal.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application is a continuation of U.S. patent application Ser. No.15/286,150 filed on Oct. 5, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/657,907 filed on Mar. 13, 2015 now U.S. Pat. No.9,467,227, which claims priority to and the benefit of U.S. ProvisionalApplication No. 61/967,254 filed on Mar. 13, 2014, each of which ishereby incorporated herein by reference in its entirety.

FIELD

Certain embodiments of the disclosure relate to semiconductor photonics.More specifically, certain embodiments of the disclosure relate to amethod and system for an optical connection service interface.

BACKGROUND

As data networks scale to meet ever-increasing bandwidth requirements,the shortcomings of copper data channels are becoming apparent. Signalattenuation and crosstalk due to radiated electromagnetic energy are themain impediments encountered by designers of such systems. They can bemitigated to some extent with equalization, coding, and shielding, butthese techniques require considerable power, complexity, and cable bulkpenalties while offering only modest improvements in reach and verylimited scalability. Free of such channel limitations, opticalcommunication has been recognized as the successor to copper links.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with the present disclosure as set forth inthe remainder of the present application with reference to the drawings.

BRIEF SUMMARY

A system and/or method for an optical connection service interface,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.

Various advantages, aspects and novel features of the presentdisclosure, as well as details of an illustrated embodiment thereof,will be more fully understood from the following description anddrawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a block diagram of a photonically-enabled integrated circuitwith an Optical Connection Service interface, in accordance with anexample embodiment of the disclosure.

FIG. 1B is a diagram illustrating an exemplary photonically-enabledintegrated circuit with Optical Connection Service interface, inaccordance with an exemplary embodiment of the disclosure.

FIG. 1C is a diagram illustrating a photonically-enabled integratedcircuit coupled to an optical fiber cable, in accordance with an exampleembodiment of the disclosure.

FIG. 2 illustrates an optical link with Optical Connection Serviceinterface, in accordance with an example embodiment of the disclosure.

FIG. 3 illustrates the operational frequency range of the OpticalConnection Service interface, in accordance with an example embodimentof the disclosure.

FIG. 4. Illustrates an example frame structure for an Optical ConnectionService interface, in accordance with an example embodiment of thedisclosure.

DETAILED DESCRIPTION

Certain aspects of the disclosure may be found in a method and systemfor an optical connection service interface. Exemplary aspects of thedisclosure may comprise, in an optical data link comprising an opticalfiber, a local control system, a first transceiver at a first end of theoptical fiber, and a second transceiver at a second end of the opticalfiber: communicating an optical data signal at frequencies greater than10 kHz utilizing the optical fiber; generating a control signal for thelocal control system at frequencies less than 10 Hz utilizing theoptical fiber; and communicating an optical service signal for anOptical Connection Service interface (OCSi) at intermediate frequenciesbetween 10 Hz and 10 kHz utilizing the optical fiber. An optical signalmay be modulated at said intermediate frequencies for the OCSi. Theoptical signal may be modulated by superimposing a modulation signalonto the biasing conditions for a laser in the first transceiver and themodulated signal may be communicated to the second transceiver utilizingthe optical fiber. The communicated modulated signal and the opticaldata signal may be detected utilizing a photodetector in the secondtransceiver. The detected optical signal may be demodulated, and anoptical power of the optical data signal may be configured based on thedemodulated signal. The optical signal may be modulated utilizing amodulator in the first transceiver, and the modulated optical signal maybe communicated to the second transceiver utilizing the optical fiber.The modulated optical signal and the optical data signal from the firsttransceiver may be detected utilizing a photodetector in the secondtransceiver. The detected optical signal may be demodulated, and anoptical power of the optical data signal may be configured based on thedemodulated signal. Optical service signals may be communicated in bothdirections in the optical fiber. An average value of the control signalmay be configured by configuring an encoding density of the OCSi signal.

FIG. 1A is a block diagram of a photonically-enabled integrated circuitwith an Optical Connection Service interface, in accordance with anexample embodiment of the disclosure. Referring to FIG. 1A, there isshown optoelectronic devices on a photonically-enabled integratedcircuit 130 comprising optical modulators 105A-105D, photodiodes111A-111D, monitor photodiodes 113A-113I, and optical devices comprisingcouplers 103A-103K, optical terminations 115A-115D, and grating couplers117A-117H. There are also shown electrical devices and circuitscomprising an Optical Connection Service interface (OCSi) control module102, a demodulator 104, amplifiers 107A-107D, analog and digital controlcircuits 109, and control sections 112A-112D. The amplifiers 107A-107Dmay comprise transimpedance and limiting amplifiers (TIA/LAs), forexample. In an example scenario, the photonically-enabled integratedcircuit 130 comprises a CMOS photonics die.

Optical signals may be communicated between optical and optoelectronicdevices via optical waveguides 110 fabricated in thephotonically-enabled integrated circuit 130. Single-mode or multi-modewaveguides may be used in photonic integrated circuits. Single-modeoperation enables direct connection to optical signal processing andnetworking elements. The term “single-mode” may be used for waveguidesthat support a single mode for each of the two polarizations,transverse-electric (TE) and transverse-magnetic (TM), or for waveguidesthat are truly single mode and only support one mode whose polarizationis TE, which comprises an electric field parallel to the substratesupporting the waveguides. Two typical waveguide cross-sections that areutilized are strip waveguides and rib waveguides. Strip waveguidestypically comprise a rectangular cross-section, whereas rib waveguidescomprise a rib section on top of a waveguide slab. Of course, otherwaveguide cross section types are also contemplated and within the scopeof the disclosure.

The optical modulators 105A-105D comprise Mach-Zehnder or ringmodulators, for example, and enable the modulation of thecontinuous-wave (CW) laser input signal. The optical modulators105A-105D may comprise high-speed and low-speed phase modulationsections and are controlled by the control sections 112A-112D. Thehigh-speed phase modulation section of the optical modulators 105A-105Dmay modulate a CW light source signal with a data signal. The low-speedphase modulation section of the optical modulators 105A-105D maycompensate for slowly varying phase factors such as those induced bymismatch between the waveguides, waveguide temperature, or waveguidestress and is referred to as the passive phase, or the passive biasingof the MZI.

In an example scenario, the low-speed phase modulation section of theoptical modulators 105A-105D may be controlled by the OCSi module 102.An OCSi may comprise a low speed (˜kb/s) service interface intended toenable communication between the two ends of an active optical cable(AOC) and/or a high speed optical link using one or more transceiverssuch as are integrated in the photonically-enabled integrated circuit130. The demodulator 104 may receive signals from the photodiodes111A-111D and demodulate signals that were modulated in the 10-10 kHzfrequency range. The demodulated signals may be provided to the OCSimodule 102 for OCSi commands, for example. In an example scenario, theOCSi module 102 may modulate optical signals for the OCSi bysuperimposing a modulation signal onto the biasing conditions for one ormore lasers in the laser assembly 101.

The outputs of the modulators 105A-105D may be optically coupled via thewaveguides 110 to the grating couplers 117E-117H. The couplers 103C-103Jmay comprise four-port optical couplers, for example, and may beutilized to sample or split the optical signals generated by the opticalmodulators 105A-105D, with the sampled signals being measured by themonitor photodiodes 113A-113H. The unused branches of the directionalcouplers 103D-103J may be terminated by optical terminations 115A-115Dto avoid back reflections of unwanted signals.

The grating couplers 117A-117H comprise optical gratings that enablecoupling of light into and out of the photonically-enabled integratedcircuit 130. The grating couplers 117A-117D may be utilized to couplelight received from optical fibers into the photonically-enabledintegrated circuit 130, and the grating couplers 117E-117H may beutilized to couple light from the photonically-enabled integratedcircuit 130 into optical fibers. The grating couplers 117A-117H maycomprise single polarization grating couplers (SPGC), polarizationsplitting grating couplers (PSGC), demultiplexing grating couplers(DMGC), and/or bi-wavelength polarization-multiplexing grating couplers(PMGC). Example PSGC and PMGC structures are described in applicationSer. No. 62/122,718 filed on Oct. 28, 2014, which is incorporated hereinby reference in its entirety. In instances where a PSGC or a PMGC isutilized, two input, or output, waveguides may be utilized. In instanceswhere a DMGC is utilized, four input, or output, waveguides may beutilized.

The optical fibers may be epoxied, for example, to the CMOS chip, andmay be aligned at an angle from normal to the surface of thephotonically-enabled integrated circuit 130 to optimize couplingefficiency. In an example embodiment, the optical fibers may comprisesingle-mode fiber (SMF) and/or polarization-maintaining fiber (PMF).

In an example embodiment, optical signals may be generated by the laserassembly 101, also sometimes referred to as a LaMP, mounted to thephotonically-enabled integrated circuit 130. The laser assembly 101 maycomprise one or more semiconductor lasers with optical elements forfocusing and directing optical signals, and may generate differentwavelengths for multi-wavelength operation of the photonically-enabledintegrated circuit 130, or a single wavelength. Accordingly, the gratingcouplers 103A and 103B may be configured for a desired wavelength. Inanother example scenario, each CW laser In 101A and 101B may comprisemultiple wavelength outputs and the grating couplers 103A and 103B maybe configured to receive multiple wavelengths.

The photodiodes 111A-111D may convert optical signals received from thegrating couplers 117A-117D into electrical signals that are communicatedto the amplifiers 107A-107D for processing. In another embodiment of thedisclosure, the photodiodes 111A-111D may comprise high-speedheterojunction phototransistors, for example, and may comprise germanium(Ge) in the collector and base regions for absorption in the 1.3-1.6 μmoptical wavelength range, and may be integrated on a CMOSsilicon-on-insulator (SOI) wafer.

The analog and digital control circuits 109 may control gain levels orother parameters in the operation of the amplifiers 107A-107D, which maythen communicate electrical signals off the photonically-enabledintegrated circuit 130. In addition, the analog and digital controlcircuits 109 may comprise a local control system that may maintain thequadrature biasing of the MZI modulators on the different channels,detect and report LOS (loss of signal) events both on the optical aswell as on the electrical ends of the link, optimize the configurationof adaptive equalization/emphasis circuitry, enable/disable on-chipre-timers, and collect and reports status information such astemperature/signal levels, and re-timer locking status.

The control sections 112A-112D comprise electronic circuitry that enablemodulation of the CW laser signal received from the splitters 103A-103C.The optical modulators 105A-105D may require high-speed electricalsignals to modulate the refractive index in respective branches of aMach-Zehnder interferometer (MZI), for example. In an exampleembodiment, the control sections 112A-112D may include sink and/orsource driver electronics that may enable a bidirectional link utilizinga single laser.

In operation, the photonically-enabled integrated circuit 130 may beoperable to transmit and/or receive and process optical signals. Opticalsignals may be received from optical fibers by the grating couplers117A-117D and converted to electrical signals by the photodetectors111A-111D. The electrical signals may be amplified by transimpedanceamplifiers in the amplifiers 107A-107D, for example, and subsequentlycommunicated to other electronic circuitry (not shown) in thephotonically-enabled integrated circuit 130.

An integrated transceiver may comprise at least three opticalinterfaces, including a transmitter input port to interface to the CWlight source, labeled as CW Laser In 101A; a transmitter output port tointerface to the fiber carrying the optical signal, labeled OpticalSignals Out; and a receiver input port to interface to the fibercarrying the optical signal, labeled Optical Signals In.

Integrated photonics platforms allow the full functionality of anoptical transceiver to be integrated on a single chip. An opticaltransceiver chip contains optoelectronic circuits that create andprocess the optical/electrical signals on the transmitter (Tx) and thereceiver (Rx) sides, as well as optical interfaces that couple theoptical signals to and from a fiber. The signal processing functionalitymay include modulating the optical carrier, detecting the opticalsignal, splitting or combining data streams, and multiplexing ordemultiplexing data on carriers with different wavelengths.

In an example embodiment of the disclosure, the OCSi module 102 may beoperable to provide control for an OCSi, which may be utilized tooptimize system parameters, such as laser power and equalization, basedon mutual knowledge of transceiver performance by the two ends of theoptical link. The OCSi may provide status and environmental informationon the modulator module useful to optimize the performance of thehigh-speed link. The OCSi may also provide adaptive optimization ofsystem parameters based on mutual knowledge of temperature of the twoends of the optical link and remote troubleshooting of hard-to-access orsoldered transceiver from the accessible end of the link. The OCSi isdescribed further with respect to FIGS. 2-4, for example.

FIG. 1B is a diagram illustrating an exemplary photonically-enabledintegrated circuit with Optical Connection Service interface, inaccordance with an exemplary embodiment of the disclosure. Referring toFIG. 1B, there is shown the photonically-enabled integrated circuit 130comprising electronic devices/circuits 131, optical and optoelectronicdevices 133, light source interfaces 135A and 135B, a chip front surface137, an optical fiber interface 139, and a CMOS guard ring 141.

The light source interfaces 135A/135B and the optical fiber interface139 comprise grating couplers, for example, that enable coupling oflight signals via the CMOS chip surface 137, as opposed to the edges ofthe chip as with conventional edge-emitting/receiving devices. Couplinglight signals via the chip surface 137 enables the use of the CMOS guardring 141 which protects the chip mechanically and prevents the entry ofcontaminants via the chip edge.

The electronic devices/circuits 131 comprise circuitry such as theamplifiers 107A-107D and the analog and digital control circuits 109described with respect to FIG. 1A, for example. The optical andoptoelectronic devices 133 comprise devices such as the couplers103A-103K, optical terminations 115A-115D, grating couplers 117A-117H,optical modulators 105A-105D, high-speed heterojunction photodiodes111A-111D, and monitor photodiodes 113A-113I.

In an example scenario, the electronic devices/circuits 131 comprise anOCSi module that may control the optical interface in an active opticalcable or other high-speed optical link in which the photonically-enabledintegrated circuit 130 comprises one end.

FIG. 1C is a diagram illustrating a photonically-enabled integratedcircuit coupled to an optical fiber cable, in accordance with an exampleembodiment of the disclosure. Referring to FIG. 1C, there is shown thephotonically-enabled integrated circuit 130 comprising the chip surface137, and the CMOS guard ring 141. There is also shown a fiber-to-chipcoupler 145, an optical fiber cable 149, and an optical sourceassemblies 147A and 147B.

The photonically-enabled integrated circuit 130 comprising theelectronic devices/circuits 131, the optical and optoelectronic devices133, the light source interface 135, the chip surface 137, and the CMOSguard ring 141 may be as described with respect to FIG. 1B, for example.

In an example embodiment, the optical fiber cable may be affixed, viaepoxy for example, to the CMOS chip surface 137. The fiber chip coupler145 enables the physical coupling of the optical fiber cable 149 to thephotonically-enabled integrated circuit 130 and may be configured toplace the optical fibers in the optical fiber cable 149 at an angle fromnormal to the chip surface 137 for optimum coupling efficiency into thegrating coupler. The angle may be defined by the grating coupler designand wavelength of light to be coupled, for example.

In an example scenario, the photonically-enabled integrated circuit 130may comprise a low-speed service interface for the optical link over theoptical fiber cable 149. The OCSi may operate in a frequency rangebetween ˜10 HZ and ˜10 kHz, which is below the optical interfacefrequency and above the control system frequency range. Thecontrol/OCSi/data signals may be communicated via the optical fibercable 149.

FIG. 2 illustrates an optical link with Optical Connection Serviceinterface, in accordance with an example embodiment of the disclosure.FIG. 2 may share any and all aspects of FIGS. 1A-1C, for example.Referring to FIG. 2, there is shown an optical link 200 comprisingtransceivers 210A and 210B coupled by optical fiber 209. Eachtransceiver 201A/201B may comprise an OCSi module 201A/201B, a lasersource 203A/203B, modulators 205A/205B, and detectors 207A/207B.

The OCSi may use the same physical medium, MAC and PHYs of thehigh-speed link. Multiplexing with high speed data may be done in thefrequency domain by selecting a band below the lower band occupation ofthe high-speed optical signal and above the control system loopsbandwidth, as illustrated in FIG. 3.

The OCSi modules 201A and 201B may comprise suitable logic, circuits,and/or code from configuring an OCSi link between the transceivers 210Aand 201B at frequencies below that of the high frequency optical signalsand above the control system frequencies. Accordingly, the OCSi modules201A and 201B may comprise controller circuitry for communicatingsignals to the lasers 203A and 2036 to modulate the output signal at afrequency range specifically for OCSi and not detected by the highfrequency circuitry. Similarly, the OCSi modules 201A and 201B mayprovide low frequency signals to the modulators 205A and 205B fortransmission of individually configurable multiple OCSi signals.

The output signals from the detectors 207A and 207B, while also used toreceive the high frequency optical signals, may also be monitored forlower frequency OCSi signals to be used by the OCSi modules 201A and201B to configure the desired component or components of thetransceivers 210A and 210B.

In an example scenario of the OCSi protocol, modulation may be performedby directly applying a low frequency modulating signal to the lasers203A/203B through their driver circuitry. In this example, all channelssharing the same laser source would carry the same OCSi signal.

In another example scenario, the signal may be applied to the low speedphase modulators (PINPM) and can be, therefore, different for eachchannel. In both examples, the signal may be encoded in such a way tominimize the disturbance on the high-speed links. This may be achievedby limiting the bandwidth of the OCSi signaling such that it is belowthe low frequency cutoff of the receiver. Furthermore, the amplitude ofthe OCSi signaling may be limited to a few least significant bits (LSBs)of a laser biasing digital-to-analog converter (DAC), for example.Finally, encoding (8B/10B) may be utilized to generate the desiredtrends (stable, increasing, decreasing) in the laser and MZI controlsignals as required by the dynamic operating conditions.

On the receiver side, the detection of the modulation can use thereceiving photodetector signal, IPHOTO, which sets a limit to themaximum data rate to half of the IPHOTO sampling rate. When lasermodulation is used on the TX side, the IPHOTO of the different channelsmay be utilized to improve the signal to noise ratio.

In an example scenario, clock recovery may be implemented in firmware orthrough a state machine. A “locked” state may be saved in a memory mapregister in the OCSi module 201A/201B for external use. In an examplescenario, the OCSi module 201A/20B may use a binary NRZ amplitudemodulation.

In terms of encoding, the basic unit of the OCSi signal is the byte (8bits), where each byte may be transcoded using the 8B/10B coding. Thechoice of one of the four possible options per symbol depends on theinput from the laser/MZI control system: symbols with higher 1/0densities may be utilized if the control signal, in average value,magnitude, or power level, is trending low/high. Otherwise the systemmay pick the best symbol sequence to keep the average value of thecontrol signal. For example, in the presence of a request from thecontrol system to increase the control signal, the encoding by the OCSimodule 201A/201B may start using symbols with higher 1 density, thusbringing the average value toward the required level. Once the desiredlevel is reached, the system will start using again symbols with zeroaverage. This may help stabilize the bias conditions of the lasersand/or modulators in the photonics transceivers.

FIG. 3 illustrates the operational frequency range of the OpticalConnection Service interface, in accordance with an example embodimentof the disclosure. Referring to FIG. 3, there is shown a frequency plotshowing range of operation of the optical link 200. Below ˜10 Hz is thecontrol system and offset compensation. The local control system mayconfigure the bias conditions for the light source, for example. Asstated previously, the local control system may maintain the quadraturebiasing of the MZI modulators on the different channels, detect andreport LOS (loss of signal) events both on the optical as well as on theelectrical ends of the link, optimize the configuration of adaptiveequalization/emphasis circuitry, enable/disable on-chip re-timers, andcollect and reports status information such as temperature/signallevels, and re-timer locking status.

The high speed optical data signal may operate in the ˜10 kHz and higherfrequencies, operating up to the switching speed of the system, in thetens of GHz range, for example. The low frequency corner of the highspeed signal may be well above the OCSi frequency range of ˜10 Hz to ˜10kHz, as illustrated in FIG. 3. Therefore, any lower frequency OCSisignals applied to the optical signals do not degrade the performance ofthe high frequency system.

FIG. 4. Illustrates an example frame structure for an Optical ConnectionService interface, in accordance with an example embodiment of thedisclosure. The optical data link 200 may utilize two differentprotocols, one “continuous” (OCSi-c) and another “on-demand” (OCSi-d).Implementation depends on the application specifics.

OCSi-c may utilize a bi-directional full duplex protocol. Transmissionmay be continuous (to allow easy clock recovery lock): when no dataneeds to be transmitted or Tx is waiting for Acknowledge, idle symbolsmay be generated. Data may then be transmitted in frames starting andending with specific delimiters. Frames can carry up to 251 symbols ofdata, for example. Each frame may have the following structure (noaddressing required), SOF-FL-FT-D-D-D . . . D-CS-EOF, as illustrated inFIG. 4.

Where SOF is the start of frame symbol, FL is the number of data bytesin the frame, FT is the type of frame (command/data), D are the payloadsymbols, CS is a checksum byte (1 or 2), and EOF is the end of framesymbol. In an example scenario, the transmitting side waits forreception of Acknowledge or Retransmit before transmitting the nextframe.

The on-demand protocol, OCSi-d, may also utilize a bi-directional fullduplex protocol. Transmission may be initiated by either of the twosides with a preamble that is used to test the link and signaltransmission capability. The other end of the link answers the preambleand may start a handshake phase to define basic communication parameters(data rate, channel used, for example). A temporary request to increaseLaMP bias to allow for a cleaner transmission may also be part of thehandshake protocol. This may have a limited impact on LaMP lifetimebecause of the very low duty cycle of communications in OCSi-d. Once thelink is established, data/commands may be transmitted in bursts. Eachburst may have the following structure: SOF-FL-FT-D-D-D . . . D-CS-EOFwith same meaning as for OCSi-c. As with OCSi-c, transmission of thenext burst will wait until an Acknowledge or a Retransmit is received.

In an example scenario, A number of key symbols may be defined andreserved in the OCSi alphabet (10B words) to identify the followingfunctions:

Start of frame (SOF)

End of frame (EOF)

Idle

Acknowledge

Retransmit

The OCSi may comprise a physical point-to-point protocol. No networkrouting or addressing is required. For transport, validation of datatransfer may be accomplished through the checksum associated with eachframe. OCSi may utilize a resend protocol based on the reception of theRetransmit in response to a frame.

A 256 byte memory map in the OCSi module 201A may be used to store oneor more received frames (depending on the length) for batch response.The pipe can be programmatically cleared from the remote side using acommand.

If the memory map is full, the Rx will keep dropping the received framesand sending Retransmit as a response to incoming frames until the bufferhas space again. This occurs unless a buffer clear command is received,which will cause all currently executing operations to abort and cleanthe buffer for accepting new requests.

For the application layer, OCSi may define a set of commands torequest/exchange basic information between the two link ends. Commandsmay be 7 bits long and fit into the FT element in the frame. The MSB ofthe FT is 0 when the command is issued and 1 for the returned data (sothat issuer can couple the response to its request). Command examplesinclude:

Status/ID information request

Remote register read

Remote register write

Clear request pipe on remote side

End of transmission (used in OCSi-d to return to normal LaMP biasing)

In an example embodiment, a method and system are disclosed for anoptical connection service interface. In this regard, aspects of thedisclosure may comprise an optical data link comprising an opticalfiber, a local control system, a first transceiver at a first end of theoptical fiber, and a second transceiver at a second end of the opticalfiber, the optical data link being operable to: communicate an opticaldata signal at frequencies greater than 10 kHz utilizing the opticalfiber, generate a control signal for the local control system atfrequencies less than 10 Hz utilizing the optical fiber, and communicatean optical service signal for an Optical Connection Service interface(OCSi) at intermediate frequencies between 10 Hz and 10 kHz utilizingthe optical fiber.

An optical signal may be modulated at the intermediate frequencies forthe OCSi. The optical signal may be modulated by superimposing amodulation signal onto biasing conditions for a laser in the firsttransceiver and the modulated signal may be communicated to the secondtransceiver utilizing the optical fiber. The communicated modulatedsignal and the optical data signal may be detected utilizing aphotodetector in the second transceiver. The detected optical signal maybe demodulated and an optical power of the optical data signal may beconfigured based on the demodulated signal. The optical signal may bemodulated utilizing a modulator in the first transceiver, and themodulated optical signal may be communicated to the second transceiverutilizing the optical fiber.

The modulated optical signal from the first transceiver may be detectedutilizing a photodetector in the second transceiver. The detectedoptical signal may be demodulated, and an optical power of the opticaldata signal may be configured based on the demodulated signal. Opticalservice signals may be communicated in both directions in the opticalfiber. An average value of the control signal may be configured byconfiguring an encoding density of the OCSi signal.

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. In other words, “xand/or y” means “one or both of x and y”. As another example, “x, y,and/or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means“one or more of x, y and z”. As utilized herein, the term “exemplary”means serving as a non-limiting example, instance, or illustration. Asutilized herein, the terms “e.g.,” and “for example” set off lists ofone or more non-limiting examples, instances, or illustrations. Asutilized herein, circuitry is “operable” to perform a function wheneverthe circuitry comprises the necessary hardware and code (if any isnecessary) to perform the function, regardless of whether performance ofthe function is disabled or not enabled (e.g., by a user-configurablesetting, factory trim, etc.).

While the disclosure has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present disclosure. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present disclosure without departing from itsscope. Therefore, it is intended that the present disclosure not belimited to the particular embodiments disclosed, but that the presentdisclosure will include all embodiments falling within the scope of theappended claims.

What is claimed is:
 1. A method for communication, the methodcomprising: in an optical data link comprising an optical fiber, acontrol system, a first transceiver at a first end of the optical fiber,and a second transceiver at a second end of the optical fiber:communicating an optical data signal at a first frequency utilizing theoptical fiber; communicating a signal for the control system at a secondfrequency, the second frequency being lower than the first frequency,utilizing the optical fiber; and communicating an Optical ConnectionService interface (OCSi) signal at a third frequency that is between thefirst and second frequencies utilizing the optical fiber.
 2. The methodaccording to claim 1, comprising modulating an optical signal at thethird frequency for the OCSi.
 3. The method according to claim 2,comprising modulating the optical signal by superimposing a modulationsignal onto biasing conditions for a laser in the first transceiver andcommunicating the modulated signal to the second transceiver utilizingthe optical fiber.
 4. The method according to claim 3, comprisingdetecting the communicated modulated signal and the optical data signalutilizing a photodetector in the second transceiver.
 5. The methodaccording to claim 4, comprising demodulating the detected opticalsignal, and configuring an optical power of the optical data signalbased on the demodulated signal.
 6. The method according to claim 2,comprising modulating the optical signal utilizing a modulator in thefirst transceiver and communicating the modulated optical signal to thesecond transceiver utilizing the optical fiber.
 7. The method accordingto claim 6, comprising detecting the modulated optical signal and theoptical data signal from the first transceiver utilizing a photodetectorin the second transceiver.
 8. The method according to claim 7,comprising demodulating the detected optical signal, and configuringoptical power of the optical data signal based on the demodulatedsignal.
 9. The method according to claim 1, wherein optical servicesignals are communicated in both directions in said optical fiber. 10.The method according to claim 1, comprising configuring an average powervalue of the control signal by configuring an encoding density of theOCSi signal.
 11. A system for communication, the system comprising: anoptical data link comprising an optical fiber, a control system, a firsttransceiver at a first end of the optical fiber, and a secondtransceiver at a second end of the optical fiber, the optical data linkbeing operable to: communicate an optical data signal at a firstfrequency utilizing the optical fiber; communicate a signal for thecontrol system at a second frequency, the second frequency being lowerthan the first frequency, utilizing the optical fiber; and communicatean Optical Connection Service interface (OCSi) signal at a thirdfrequency that is between the first and second frequencies utilizing theoptical fiber.
 12. The system according to claim 11, wherein the opticaldata link is operable to modulate an optical signal at the thirdfrequency for the OCSi.
 13. The system according to claim 12, whereinthe optical data link is operable to modulate the optical signal bysuperimposing a modulation signal onto biasing conditions for a laser inthe first transceiver and communicate the modulated signal to the secondtransceiver utilizing the optical fiber.
 14. The system according toclaim 13, wherein the optical data link is operable to detect thecommunicated modulated signal and the optical data signal utilizing aphotodetector in the second transceiver.
 15. The system according toclaim 14, wherein the optical data link is operable to demodulate thedetected optical signal, and configure an optical power of the opticaldata signal based on the demodulated signal.
 16. The system according toclaim 12, wherein the optical data link is operable to modulate theoptical signal utilizing a modulator in the first transceiver andcommunicate the modulated optical signal to the second transceiverutilizing the optical fiber.
 17. The system according to claim 16,wherein the optical data link is operable to detect the modulatedoptical signal and the optical data signal from the first transceiverutilizing a photodetector in the second transceiver.
 18. The systemaccording to claim 17, wherein the optical data link is operable todemodulate the detected optical signal, and configure optical power ofthe optical data signal based on the demodulated signal.
 19. The systemaccording to claim 12, wherein the optical data link is operable toconfigure an average value of the control signal by configuring anencoding density of the OCSi signal.
 20. A system for communication, thesystem comprising: an optical data link comprising an optical fiber, acontrol system, a first transceiver at a first end of the optical fiber,and a second transceiver at a second end of the optical fiber, theoptical data link being operable to: communicate an optical data signalat a first frequency utilizing the optical fiber; generate a signal forthe control system at a second frequency, the second frequency beinglower than the first frequency, utilizing the optical fiber; andcommunicate an Optical Connection Service interface (OCSi) signalutilizing the optical fiber, wherein the optical service signal isgenerated by applying a modulation signal to the optical data signal atfrequency between the first and second frequency.